Microelectronic-device substrate assemblies are typically semiconductor substrates used in the manufacturing of semiconductor devices, field emission displays and other microelectronic devices. In a typical application for manufacturing semiconductor devices, the substrate assemblies are semiconductor wafers upon which a plurality of individual devices are formed in several processing steps. Memory devices, for example, are fabricated on 6-12 inch wafers that provide enough surface area to fabricate several hundred individual memory devices on a single substrate assembly. After the circuits of the individual devices have been constructed, the substrate assembly is cut to separate the devices from one another, and then the individual devices are often packaged for mounting to a printed circuit board assembly.
One aspect of manufacturing or using substrate assemblies is handling the substrate assemblies in processing machines. Substrate assemblies are fairly delicate structures that may chip or crack, and the integrated circuits of the individual devices are very delicate structures that may be damaged or destroyed by static electricity. To protect the substrate assemblies during certain stages of processing, the substrate assemblies are attached to a backing film that is stretched over a metal frame to avoid directly contacting the substrate assemblies with the handling equipment. In a typical fabrication process, for example, substrate assemblies are coupled to frames by the backing film for processing in a dicing machine that cuts the substrate assemblies to separate the devices from one another. Additionally, because the backing film may stretch and cause difficulties in cutting the substrate assemblies in the dicing machines, the frames and the substrate assemblies are placed in an "expander" machine that shrinks the backing film until it is taut. Existing expander machines, however, have many drawbacks that make it difficult to handle substrate assemblies.
FIG. 1 is an isometric view partially illustrating an existing expander machine 10 that has a processing station 20, a loader 30 and a cassette 50. The processing station 20 has a plate assembly with a first plate 22 and a second plate 24 spaced apart from one another by a gap 26. A number of posts 27 attached to the table 12 support the first and second plates 22 and 24 to position the plate gap 26 at a desired elevation with respect to the cassette 50. The processing station 20 has a first side 28 facing the loader 30 and a second side 29 facing the cassette 50.
The loader 30 is mounted to a base 31 proximate to the first side 28 of the processing station 20. The loader 30 has a housing 32, a motor 33 attached to the housing 32, and a spring-loaded tape assembly 34 with a thin metal tape 36 that projects from the housing 32. The tape 36 includes a plurality of holes 38 arranged in a line along the length of the tape 36 to receive the teeth of a sprocket 39 attached to an output shaft of the motor 33. A clamp 40 is attached to the end of the tape 36. The clamp 40 has a pair of clips 42, and each clip 42 has an upper finger and a lower finger that are biased toward one another.
In operation, the motor 33 turns the sprocket 39 to move the tape 36 and the clamp 40 along a processing path P through the gap 26 between the first and second plates 22 and 24. For example, to remove a selected substrate assembly from the cassette 50, the motor 33 drives the tape 36 out of the tape assembly 34 until the clamp 40 engages a frame 52 to which the selected substrate assembly is attached via a backing film. The motor 33 then reverses the rotation of the sprocket 39 to pull the frame 52 and selected substrate assembly out of the wafer cassette 50 and into the plate gap 26 between the first and second plates 22 and 24 at the processing station 20. The spring-loaded tape assembly 34 accordingly recoils a portion of the tape 36 in a manner similar to a tape measure. After the substrate assembly has been processed at the processing station 20, the motor 33 rotates the sprocket 39 to drive the tape 36 from the tape assembly 34 until the frame 52 and selected substrate assembly are replaced in the wafer cassette 50. The motor 33 then reverses the rotation of the sprocket 39 very quickly to disengage the clips 42 from the frame 52 and retract the clamp 40 to the loader 30.
One drawback with the expander machine 10 is that the loader 30 may not accurately drive the tape 36 and the clamp 40 along the processing path P to accurately pick up, position and release the frames 52 for processing the substrate assemblies. More particularly, the thin metal tape 36 often cracks in a line between the holes 38. The teeth of the sprocket 39 may accordingly pass through the cracks between the holes 38 in the thin metal tape instead of pushing against the portion of the tape 36 between the holes 38. The cracks in the tape 36 between the holes 38 typically develop to a point at which the loader 30 is inoperable and the tape assembly 34 must be replaced. Repairing the loader 30, however, results in down-time for the expander machine 10. Thus, the durability of the tape assembly 34 is a significant drawback in handling microelectronic-device substrate assemblies in the expander machine 10.
Another problem of the expander machine 10 is that the clamp 40 may hit one of the first and second plates 22 and 24 of the processing station 20 as the loader 30 drives the tape 36 from the loader 30 to the cassette 50. This problem arises because the clamp 40 causes the thin tape 36 to bend downward as the clamp 40 moves from the loader 30 toward the processing station 20. The vertical displacement of the clamp 40 accordingly increases with increasing distance from the loader 30 such that the height of the loader 30 is generally adjusted at the initial set-up so that the clamp 40 passes through the plate gap 26 on both the first and second sides 28 and 29 of the processing station 20. Moreover, as the thin tape 36 wears and cracks develop between the holes 38, the bend radius of the tape 36 changes over time causing the vertical displacement of the clamp 40 along the processing path to also change. The clamp 40 may even hit one of the first or second plates 22 or 24 when the tape 36 wears down after a period of use. When this occurs, the height of the loader 30 must be readjusted to compensate for the changes in the integrity of the tape 36. Adjusting the height of the loader 30 so that the clamp 40 passes through the gap 26 of the processing station 20 is a difficult and time-consuming process because it is generally a trial-and-error procedure. Therefore, constantly adjusting and readjusting the loader 30 so that the clamp 40 can "shoot the gap" of the plate gap 26 also causes down-time for the expander machine 10.
Still another drawback of the expander machine 10 is that the clamp 40 may not positively engage or disengage the frames 52. The frames 52 wear down the interior surfaces of the clips 42 causing a gap to form between the fingers of each clip 42. After the frames 52 wear down the interior surfaces of the clips 42, the clamp 40 may not sufficiently engage a frame 52 to pull the frame 52 out of the cassette 50. Therefore, the durability of the clamp 40 also presents another operating concern of using the expander machine 10.